This invention relates to a pressure actuated assembly which can extend and retract, and more particularly to a pressure actuated assembly extendable by fluid pressure and retractable by spring action.
A fluid pressure actuated assembly is commonly used in a pressure gauge, a height-adjustable chair, and the like. It typically employs a hydraulic cylinder in which a piston moves. The hydraulic cylinder type assemblies suffer from the following disadvantages:
(1) The space between the piston and the cylinder wears easily, even if various oil rings are provided therebetween.
(2) When substantial liquid pressure is applied to the interior of the hydraulic cylinder, the resulting leakage of hydraulic oil may occur in the hydraulic cylinder, causing inaccurate travel of the piston.
(3) When a movable mechanical component is associated with the hydraulic cylinder, if the displacement of the mechanical component is dependent on the travel of the piston, the leakage of the hydraulic oil in the hydraulic cylinder will cause inaccurate displacement of the mechanical component.